5:15 PM - 7:15 PM
[SGD02-P09] GSI Global solution of VLBI observations
Keywords:VLBI, Global solution, Earth Orientation Parameter (EOP), Terrestrial Reference Frame (TRF)
Introduction
The Geospatial Information Authority of Japan (GSI) operates the VLBI antenna at Ishioka Geodetic Observing Station, Ishioka, Japan. We conduct international VLBI observations coordinated by the International VLBI Service for geodesy and Astrometry (IVS) to contribute to construction of the Global Geodetic Reference Frame (GGRF) and to determine the position of Japan on the global reference frame.
VLBI stations participate in the observation based on the schedule arranged by the IVS. Observed data are correlated and the results of primary solution are stored as databases.
We conduct global analysis to precisely determine the 3D positions of stations on Terrestrial Reference Frame (TRF) and Earth Orientation Parameters (EOPs) including UT1 using these databases (Kokado et al., 2006). GSI estimates the global solution biannually in March and September, and release them on our website.
Overview of global solutions
In global analysis, we download the databases from the IVS Data Centers and perform global analysis using multiple observation databases for various networks. For the analysis, we usesoftware ”CALC/SOLVE” developed by NASA/GSFC. We set appropriate a-priori values and constraint conditions for the observing station position, velocity, and radio source position, and perform the analysis. There are two types of parameters to estimate in a global solution: "global parameters" and "local parameters". The global parameters are common to all sessions in the databases, and include the station positions, rates of change of the station positions (velocity field), radio source positions (declination/right ascension), and antenna axis offsets. The local parameters are estimated in each session, including EOPs, zenith humid atmosphere delay, time-based changes of baseline relative to the reference station, atmospheric gradient, and clock offset.
Result of global solution
In our global analysis in September 2024, we analyzed databases of over 7,000 VLBI observations from 1980 to September 2024.
Figure 1 shows the station velocities estimated through the analysis plotted on a map. This indicates the average motion of the stations during the analysis period, and it is consistent with each plate motion. Figure 2 shows the results of UT1. It is one of the EOPs which represents the state of the Earth's rotation.
In this presentation, we report on the method of our global analysis and show our latest solution in March 2025, and we also give an update on our study for improving accuracy of solutions.
(References)
KOKADO, K., MACHIDA, M., and TAKASHIMA, K., Highly Precise Determination of Earth Orientation Parameter by VLBI Global Solutions, Bulletin of the GSI, 110, p. 11-18 (in Japanese).
The Geospatial Information Authority of Japan (GSI) operates the VLBI antenna at Ishioka Geodetic Observing Station, Ishioka, Japan. We conduct international VLBI observations coordinated by the International VLBI Service for geodesy and Astrometry (IVS) to contribute to construction of the Global Geodetic Reference Frame (GGRF) and to determine the position of Japan on the global reference frame.
VLBI stations participate in the observation based on the schedule arranged by the IVS. Observed data are correlated and the results of primary solution are stored as databases.
We conduct global analysis to precisely determine the 3D positions of stations on Terrestrial Reference Frame (TRF) and Earth Orientation Parameters (EOPs) including UT1 using these databases (Kokado et al., 2006). GSI estimates the global solution biannually in March and September, and release them on our website.
Overview of global solutions
In global analysis, we download the databases from the IVS Data Centers and perform global analysis using multiple observation databases for various networks. For the analysis, we usesoftware ”CALC/SOLVE” developed by NASA/GSFC. We set appropriate a-priori values and constraint conditions for the observing station position, velocity, and radio source position, and perform the analysis. There are two types of parameters to estimate in a global solution: "global parameters" and "local parameters". The global parameters are common to all sessions in the databases, and include the station positions, rates of change of the station positions (velocity field), radio source positions (declination/right ascension), and antenna axis offsets. The local parameters are estimated in each session, including EOPs, zenith humid atmosphere delay, time-based changes of baseline relative to the reference station, atmospheric gradient, and clock offset.
Result of global solution
In our global analysis in September 2024, we analyzed databases of over 7,000 VLBI observations from 1980 to September 2024.
Figure 1 shows the station velocities estimated through the analysis plotted on a map. This indicates the average motion of the stations during the analysis period, and it is consistent with each plate motion. Figure 2 shows the results of UT1. It is one of the EOPs which represents the state of the Earth's rotation.
In this presentation, we report on the method of our global analysis and show our latest solution in March 2025, and we also give an update on our study for improving accuracy of solutions.
(References)
KOKADO, K., MACHIDA, M., and TAKASHIMA, K., Highly Precise Determination of Earth Orientation Parameter by VLBI Global Solutions, Bulletin of the GSI, 110, p. 11-18 (in Japanese).